Transparent ceramic garnet scintillator detector for positron emission tomography

Abstract

In one embodiment, a method includes forming a powder having a composition with the formula: A h B i C j O 12 , where h is 3±10%, i is 2±10%, j is 3±10%, A includes one or more rare earth elements, B includes aluminum and/or gallium, and C includes aluminum and/or gallium. The method additionally includes consolidating the powder to form an optically transparent ceramic, and applying at least one thermodynamic process condition during the consolidating to reduce oxygen and/or thermodynamically reversible defects in the ceramic. In another embodiment, a scintillator includes (Gd 3-a-c Y a ) x (Ga 5-b Al b ) y O 12 D c , where a is from about 0.05-2, b is from about 1-3, x is from about 2.8-3.2, y is from about 4.8-5.2, c is from about 0.003-0.3, and D is a dopant, and where the scintillator is an optically transparent ceramic scintillator having physical characteristics of being formed from a ceramic powder consolidated in oxidizing atmospheres.

What is claimed is: 
     
       1. A method, comprising:
 forming a powder comprising a composition with the formula: A h B i C j O 12 , wherein h is 3 ±10%, i is 2±10%, and j is 3±10%, wherein A includes one or more rare earth elements, B includes aluminum and/or gallium, and C includes aluminum and/or gallium; 
 consolidating the powder to form an optically transparent ceramic; 
 applying at least one thermodynamic process condition during the consolidating to reduce oxygen related defects and/or thermodynamically reversible defects in the ceramic; and 
 annealing the optically transparent ceramic in an oxygen containing atmosphere at a temperature ranging from about 1000° C. to about 1900° C. 
 
     
     
       2. The method as recited in  claim 1 , wherein A is selected from the group consisting of: yttrium, gadolinium, lutetium, lanthanum, terbium, praseodymium, neodymium, cerium, samarium, europium, dysprosium, holmium, erbium, ytterbium, and combinations thereof. 
     
     
       3. The method as recited in  claim 1 , wherein A comprises gadolinium (Gd) and yttrium (Y), wherein a ratio of Gd to Y is in a range from about 1:1 to about 10:1. 
     
     
       4. The method as recited in  claim 3 , wherein the composition comprises at least one dopant configured to act as an activator, wherein the dopant is selected from the group consisting of: Cu + , Ag + , Au + , Pb 2+ , Bi 3+ , In + , Sn 2+ , Sb 3+ , Pr 3+ , Yb 2+ , Nb 5+ , Ta 5+ , W 6+ , Ce 3+  and combinations thereof. 
     
     
       5. The method as recited in  claim 4 , wherein the dopant is present in an amount ranging from about 0.01% to about 10% of a total combined amount of Gd and Y. 
     
     
       6. The method as recited in  claim 1 , wherein the composition comprises the formula (Gd 3-a-c Y a ) x (Ga 5-b Al b ) y O 12 D c , wherein a is from about 0.05 to about 2, b is from about 1 to about 3, x is from about 2.8 to about 3.2, y is from about 4.8 to about 5.2, c is from about 0.003 to about 0.3, and D is a dopant. 
     
     
       7. The method as recited in  claim 6 , wherein D includes cerium. 
     
     
       8. The method as recited in  claim 7 , further comprising forming Ce 4+  in the optically transparent ceramic, wherein from 0% to about 50% of the cerium in the optically transparent ceramic is Ce 4+ . 
     
     
       9. The method of  claim 6 , wherein at least one divalent aliovalent dopant is added to the composition prior to consolidating the powder to form the optically transparent ceramic. 
     
     
       10. The method as recited in  claim 9 , wherein the divalent aliovalent dopant is selected from the group consisting of: Mg 2+ , Sr 2+ , Ba 2+ , B 3+  and combinations thereof. 
     
     
       11. The method as recited in  claim 1 , wherein forming the powder comprises flame spray pyrolysis of one or more liquid precursor materials. 
     
     
       12. The method as recited in  claim 1 , wherein forming the powder comprises a combustion synthesis process. 
     
     
       13. The method as recited in  claim 1 , wherein forming the powder comprises at least one processing step to achieve particles having a size less than about 500 microns, the at least one processing step comprises milling the particles. 
     
     
       14. The method as recited in  claim 1 , wherein the thermodynamic process condition includes at least two of: temperature, gas atmosphere, and pressure. 
     
     
       15. The method as recited in  claim 1 , wherein the consolidating comprises sintering the powder in a second oxygen containing atmosphere at a temperature ranging from about 1200° C. to about 1700° C. 
     
     
       16. The method as recited in  claim 15 , wherein the second oxygen containing atmosphere comprises one or more noble gases. 
     
     
       17. The method as recited in  claim 15 , wherein the oxygen containing atmosphere consists essentially of oxygen. 
     
     
       18. The method as recited in  claim 1 , further comprising, prior to the consolidating: pressing the powder into a green body; and calcining the green body at a temperature ranging from about 500° C. to about 1500° C. 
     
     
       19. The method as recited in  claim 1 , further comprising spray-drying a slurry comprising the powder prior to consolidating the powder. 
     
     
       20. The method as recited in  claim 19 , the spray-drying comprising atomizing the slurry in an inert atmosphere and at a temperature of about 200° C. 
     
     
       21. The method as recited in  claim 1 , further comprising filtering or sieving the powder using a filter or sieve having a pore diameter less than or equal to about 50 microns. 
     
     
       22. The method as recited in  claim 1 , wherein A comprises gadolinium (Gd) and yttrium (Y), wherein a ratio of Gd to Y is in a range from about 2:1 to about 10:1. 
     
     
       23. The method as recited in  claim 1 , wherein at least one of applying the at least one thermodynamic process during the consolidating, and annealing the optically transparent ceramic in the oxygen containing atmosphere results in the optically transparent ceramic exhibiting a rise time component less than or equal to about 2 ns, and/or a timing resolution less than or equal to about 350 ps. 
     
     
       24. A method, comprising:
 forming a powder comprising a composition with the formula: A h B i C j O 12 , wherein h is 3±10%, i is 2±10%, and j is 3±10%, wherein A includes one or more rare earth elements, B includes aluminum and/or gallium, and C includes aluminum and/or gallium; 
 consolidating the powder to form an optically transparent ceramic, wherein the consolidating comprises applying at least one thermodynamic process condition during the consolidating to reduce oxygen and/or thermodynamically reversible defects in the ceramic by sintering the powder in an oxygen containing atmosphere at a temperature ranging from about 1200° C. to about 1700° C.; and 
 annealing the optically transparent ceramic in an oxygen containing atmosphere at a temperature ranging from about 1000° C. to about 1900° C. 
 
     
     
       25. A radiation detection system, comprising:
 at least one optically transparent ceramic scintillator comprising the formula (Gd 3-a-c Y a ) x (Ga 5-b Al b ) y O 12 D c , wherein a is from about 0.05 to about 2, b is from about 1 to about 3, x is from about 2.8 to about 3.2, y is from about 4.8 to about 5.2, c is from about 0.003 to about 0.3, and D is a dopant, 
 wherein the optically transparent ceramic scintillator has physical characteristics of being formed from a ceramic powder consolidated in oxidizing atmospheres, and 
 wherein the optically transparent ceramic has substantially reduced oxygen related defects and/or thermodynamically reversible defects. 
 
     
     
       26. The radiation detection system of  claim 25 , comprising a photodetector configured to detect light pulses from the optically transparent ceramic scintillator, wherein the photodetector comprises at least one of a photomultiplier and a silicon photomultiplier. 
     
     
       27. The radiation detection system of  claim 25 , wherein the radiation detection system is a positron emission tomography system. 
     
     
       28. The radiation detection system of  claim 25 , wherein the radiation detection system is selected from the group consisting of: a computed tomography system (CT); a positron emission tomography system (PET); a single-photon emission computed tomography system (SPECT); and combinations thereof. 
     
     
       29. The scintillator as recited in  claim 25 , wherein particles of the ceramic powder are coated with one or more organic compounds. 
     
     
       30. A scintillator, comprising:
 (Gd 3-a-c Y a ) x (Ga 5-b Al b ) y O 12 D c , wherein a is from about 0.05 to about 1, b is from about 1 to about 3, x is from about 2.8 to about 3.2, y is from about 4.8 to about 5.2, c is from about 0.003 to about 0.3, and D is a dopant, 
 wherein the scintillator is an optically transparent ceramic scintillator, and 
 wherein the optically transparent ceramic scintillator has physical characteristics of being formed from a ceramic powder consolidated in oxidizing atmospheres so as to reduce one or more of: oxygen related detects and thermodynamically reversible defects. 
 
     
     
       31. The scintillator as recited in  claim 30 , wherein the scintillator has a rise time component less than or equal to about 2 ns, and/or a timing resolution less than or equal to about 350 ps. 
     
     
       32. The scintillator as recited in  claim 30 , wherein D comprises Ce 3+  and Ce 4+ , wherein a level of transparency of the scintillator is based on an amount of at least one of Ce 3+  and Ce 4+ .